With increase of the number of users and emergence of demand for high bandwidth, in one to five years, currently deployed access networks such as GPON (Gigabit-capable Passive Optical Network, gigabit-capable passive optical network) and EPON (Ethernet Passive Optical Network, Ethernet passive optical network) will have to be upgraded to PON (Passive Optical Network, passive optical network) networks having larger capacities. However, considering the investment and fixed assets placed in deployment of such access network as GPON and EPON, for sake of return on the current investment and increase of the coverage and transmission capacity of the access network, a nested TDM (Time-division Multiplexing, time-division multiplexing) PON may be employed.
With respect to the current PON, for example, GPON, dynamic bandwidth allocation refers to a process that an ONU (Optical Network Unit, optical network unit) and a correlated T-CONT (Transmission Container, transmission container) directly or indirectly request uplink bandwidth dynamically; and, arranges bandwidth according to the real-time state of the ONU, and dynamically adjusts the bandwidth value granted to the ONU in the manner that an OLT monitors idle frames or the ONU reports real-time state of uplink service traffic to the OLT (Optical Line Terminal, optical line terminal device). In this way, the manner of allocating ONU uplink bandwidth by the OLT not only ensures that uplink services of various ONUs are not subject to conflicts, but also fully utilizes bandwidth resources.
During the state report-based dynamic bandwidth allocation, both the real-time state of the traffic reported by the ONU and the uplink bandwidth allocation by the OLT use the transmission container T-CONT as granularity. Each T-CONT may be considered as a logical cache, and each logical cache stores user service data having similar QoS requirements. With respect to each T-CONT of the ONU, a dynamic bandwidth allocation function module of the OLT collects in-band uplink dynamic bandwidth reports, determines occupancy of the T-CONT, and acquires the real-time state of the uplink service traffic. The OLT generates a bandwidth mapping table according to the occupancy, available bandwidth resources, and agreement signed with a user. The bandwidth mapping table is transmitted to the ONU by means of downlink in-band transmission, to provide guidance for the ONU to implement uplink transmission.
During the implementation of the present disclosure, it is found that the prior art has at least the following problems:
The conventional bandwidth allocating methods are directed to a single-stage PON network, and therefore optimal quality of service is assured for the user service data in the single-stage PON. However, a nested PON has two stages of PON network structures, and optimal quality of service in each single-stage PON may not ensure that the overall quality of service in the two-stage PON network is optimal. This is because the data on which importance is placed in one stage of PON, especially the service data having a lower priority, may not be attached with importance in another stage of PON, and may even be discarded. As a result, the importance placed by the previous stage of PON is of no significance, and therefore the overall quality of service deteriorates.